'We must describe', says
Plato, 'how
timocracy changes into
oligarchy .. Even a blind man must see how it changes .. It is the treasure house that ruins this
constitution. They' (the timocrats) 'begin by creating opportunities for showing off and spending
money, and to this end they twist the laws, and they and their wives disobey them ..; and they try to outrival one another.' In this way arises the first
class conflict: that between virtue and money, or between the old-established ways of feudal simplicity and the new ways of wealth. The transition to oligarchy is completed when the rich establish a law that '
disqualifies from public office all those whose means do not reach the stipulated amount. This change is imposed by force or arms, should threats and
blackmail not succeed ..'
Karl Popper, The Open Society and Its Enemies, taken from chapter 4 on Change and Rest. Parts in quotes are taken directly from Plato, boldfaced emphasis is mine.
Perhaps its a trite observation but according to this definition America is an oligarchy rather than a democracy, of course Plato would have been happy about this as he considered democracy to be better only than tyranny.